Apparatus for the manufacture of rubber tubes



ug. 7, 1934. A. A. GLIDDEN x-:T Al.

Filed oct. 1o, 1929 j? W, e z @30745 Z/7fgd .2% mi@ 77:07;

A. A. GLIDDEN ET Ax. 1,969,071

APPARATUS FOR THE MANUFACTURE OF RUBBERTUBES Filed Oct. 10, 1929- 3Sheets-Sheet 2 Aug. 7, 1934.

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Aug 7, 1934.` A. A. GLIDDEN ET AL 1,969,071

APPARATUS FOR THE MANUFACTURE. OF RUBBER TUBES Filed Oct. l0, 1929 3Sheets-Shes?l 3 Patented ug. 7, 1934 RUBBER TUBES Alfred A. Glidden andThomas-'M.Knowland,

Watertown, Mass., ass'ign'ors to Hood Rubber Company, Inc., Watertown,Mass., a corporation of Delaware Application October 10, 1929,

serial No. n 398,629

9 claims. (ci. 18-24) f vThis invention relates to the manufacture ofvulcanized rubber tubes, particularly of Vinner tubes for pneumatictyres, and has for its object the construction of tubes of thischaracter rdirectly from latex, orA its concentrated modication,revertex, by agglomeration of the individual solid particles suspendedin the water emulsion by progressive and regulated evaporation of thesaid Water which conserves'the association of the component of said unitparticles, as distinguished from coagulation, as by means of acidagents, which is characterized by extrusion from the rubber coagulumywith the waterr of emulsion, of the proteids, sugars, etc., normallyassociated with the rubber particles.

The invention presents three aspects, namely: process, product, andapparatus, and is herein described in all three. ances ofthe elements orfactors of apparatus, in their lnecessary functional order andsuccession, are steps of the process. The process or series of stepsrequires the essential elements of the apparatus,l as described herein,for its performance. The performance of the essential elements ofapparatus, and the process therein involved, inevitably results/in theproduct herein described.

In its process-aspect, the invention is characterized by application ofa foundation lm of rubber-emulsion (with usual composition-ingredientsdistributed through it, such as zinc oXid, sulfur, an accelerator) toamandrel, the material of which is preferably afmetal inert to latex, andthe vsurface non-porous and impenetrable, partially drying the said lm,under conditions which maintain uniform thickness of the film, applyinga second lm coating on the foundation film before the exposed surface ofthe latter has, by loss of Water, reached irreversibility, ypartiallydrying the second or outer nlm under dation nlm, applying a third filmto the still reversible material of the second, and so on, until thedesired body or thickness of tube has accumulated, when the tube,supported by the mandrei,` may be thoroughly dried, then stripped fromthe mandrel, and vulcanized; or vulcanized onV themandrel and afterwardstripped.

In its apparatus aspect, the invention is characterized by means forapplying, in succession and superposition, upon a mandrel, coatings of alatex composition, means for immersing and. emerging, in alternation,the lower segment or.

limb of the mandrel in a poolr of the emulsion,

and means for changing the rate of rotation lof The respective perform-`conditions similar to those imposed on the founthe mandrel on its axisto s uit the conditions, respectively, for applying and setting eachcoatf ing of emulsion. Y Y

In its product aspect, the invention is exemplified by a tube of latexrubber (or rubber com,- position) which, though built to desiredthickness by accumulation ofsuccessive latex emulsion coatings, is freefrom lamination, an integer in structure, homogeneous, and free fromvany grain effect; a tube which, when completed, vconserves inritsconstitution the Whole of the ingredients in suspension in the originalemulsion, and the characters of the original rubber unit particles,altered vonly by aggregation and coalescence, consequent on eliminationof the water of4 suspension, and by vulcanization.

Herein, the word latex is employed as meaningreither normal latex, orits reversible concentrate, revertex.

' diagrammatic.

Fig. 1 illustras the modein which successive film coatings of preparedrevertex composition are applied in building a tube; Y

Fig. 2 the ltube mandrel removed `from Contact with thecomposition-supply;

Fig. 3 a segment in section of mandrel and first nlm coating; Y l V Fig.4 a similar segment-section of mandrel, iirst coating and secondcoating;

Fig, l5 is an end-elevational view of apparatus comprising the elementsillustrated in Figs. 1 and 2;

Fig. 6 is a view, partly in front elevation, partly in section, of thesame;

Fig.7 is a section on line 7-,7 of Fig. 5; and

Fig. Y8 isa wiring diagram. 95

First referring to the elementary Figs. 1 to 4, inclusivez-,liquidlatexA composition R, (of whatever concentration may be desired,preferablyVv more concentrated than normal latex)v containing, forinstance,.-zinc oxidffinely divided sulfur, ,and anaccelerator, isplacedin a trough T. .A tubemandrel, lM, of aluminumor other smoothlyVvpolished surface, isv mounted on cen- ,tersv above thetrough,substantially parallel lwith the levelsurfacey of the composition.

Mechanical adjuncts (not shown in Figs.`

1 andI 2,) l are Aprovided whereby the mandrelv M andA trough T may ber4made to approach or recede from each other While main- 11M]` tainingthe said parallel relation. Preferably this will be accomplished byraising and lowering the trough T.

The first film coating of latex composition is applied by raising thetrough T until a. narrow segmentv of ,they mandrelA is immersed; in the.composition. Before making this contact thesurface of the composition Rshould be cleared of any skin that may have formed upon it. At or;

just before the contact is made, the mandrel M is started to rotate onits axis, but4 rather slowly, say at a surface velocity aboutseventy-five inches per minute.

mandrel and composition quickly: broken as by lowering the trough T, andimmediately after emersion the mandrel is causedto rotate on itsv axis(which is kept horizontal) at a much higher speed than before; thenumber of rotations per' minute may vary within `quite wide limits,provided-thealte'rnation of any given point on the mandrel'surace;betweenrascent andv descent, be

sufficiently frequent to prevent the lm or enveiopeof latexlfrom runningcircumferentially of the mandrel to produce irregularities in thicknessofthe film. For this-'purpose a surface velocity of about one hundredand-'eighty inchesper minute has been found-suitable.Y The coatedmandrel is keptrotating-.atV the relatively higlr ratev until theYevaporation of the water fromv ythe coating of composition has so far'reduced the water-percentage astoproduce anv increase of viscosity. andplasticitytherein which practicallyvxes the coating` iii-uniformthickness, but not so far-Vas to produceirreversibility in thecomposition at andnear` its exposed surface, if, as will'be-almostinvariably the case, the composition layeron the mandrel is to be builtup`v mandrel, but alsobecause thetime of exposure to drying air can bemore accurately determinedv when the extraction offwater from thecomposition iilm is effectedinoneradial direction-only@ The foundation.coatingv having-beenvset; as

above 'described the' application or"l the nextcoating follows. Themandrel M, now carrying a layer oi composition setto apracticallyirmconsistency, which, however,` retains enoughvof the kemulsion liquid l'to preserve f the reversible character at the exposedl surface,` isagain broughty into segment-immersion' relation with he compositionsupply R inl trough T, its rate of-rotation being1 slowedldown to give asurface' velocity of about seventy-iive inches perminute, so that thesecond lm coating shall be evenly taken up. Just prior to theapplication oi' the SecOndcGating the condition of-'the rstis asillustrated in Fig.: 3 (the coating-thickness in this gure andi in- Fig.4'being exaggerated). Thewater of lthe supply-emulsion is migratinginftliedirection of the arrow through the'coat? ing Ll, and the intimacyof agglomerationof the suspended Vsolids in the film increases in thesame direction. The applicationV of the 'nextv coatings L2 over L1 (Fig.4)V stops evaporation-' When the mandrel has made one full rotation,the-'contact between;

from the surface of coating L1', in which the remaining Water proceedstoward uniform redistribution. At the same time water from L2 migratesinto L1, reversing the progress of agglomeration of the revertex solids.The mandrelM; being as before immersedirom thegcomposition supply R, andgiven its higher rate of rotation, water-evaporation from the outersurface of coating L2 begins, and presently the migration of Waterinrboth L1 and L2 proceeds centripetally; the momentry reversion ofymigra tion from L2 to L1 will havev integrated the two coatings., sothat no-'distinction of lamination will thereafterdevelop between them.

The foregoingialternations of envelope-application andv evaporationhaving been continued untilthedesired thickness of tube is acquired theagglomerated material o n the mandrel will be dried thoroughly, or untilit is in condition `for vulcanization; the mandrel with the uncuredtubeon it may then -be placed ina suitable vuieanizingY apparatus, andcured ;v or the tube-may be strippedA rst and vulcanized later.If-thetube is to be 'used'as an inner tube of a pneumatic tyre, thepreferred modeof'manufacture will comprise attachment of a valvebaseto-the-unvulcanized tube Ywhile on the mandrel, removall of the tubefrom the mandrel by the aid of compressedair, attachment' of thevalve,splicing the ends ofthe tube, inflation and vulcanization/in any-usual'manner- A Observed advantages of the process above describedlare: That each layer of the supply` emulsion, attachedto the formrepresented'by the mandrel (with or without previously setk layers)being quite thin, is by the air-drying to-which it is'subjected reducedto avery nearlyl homogeneous condition of agglomerationof 'thelatexsolids. (as distinguished from the otherl solids which enterl into'theivulcanizable comeratingfcolloidal'net of latex-solids) so that .in

a tube-.of considerable wall-thickness, produced by theaccumulation ofVthiny layers, the struc-.

ture is. homogeneous rand the residual Water-v smallin percentage-anduniformly distributed'.

A relatively short period of air drying4 of'the l completedy tube, attemperatures belowA boiling point suiiices.. to` eliminate thisrresidual water; thusthe tube is-soon incondition for vulcaniza tion andcan becured without danger of any cellular sponge. formation in` itswall. Tubes4 formed in the manner above described are freeromany..""grain are. exceptionally strong and resistantfto penetration,tearing, or checking.

distinction. between agglomerationk and:`V

coagulation of latexiparticles is `well'recognized,v

though` the. twoA changes in physical state' may be. sequent: inr therelatively. abrupt transformation tocoagulation. Transformation of alatex emulsion into. a; virtually solid vconsistency by.

Vagglomerationbyvthe above described agency of spontaneous` evaporationvis a relatively slow andgentle process; its progressive-stagesare.difficult to.v detectv directlybut may Withicon'- iidence be inferredibyobserving. thek subsidence z of i Brownian .movement in f test samples ftakenr` at successive. intervals. .It is .believe'dj andi the qualitiesof agglomerated'latex confirm .the'belief-,ithatthis-mode oftransformationl of latex to a `virtualV solidA conserves intheconstituent particles-their originally associatedconstituents, and doesnot break the unit-aggregates of latex particles.V 'The strength` andtoughnessjof the resultant product; as in atube made as'aboveA thesemotors Vreceiving their current from a'= described, as well as othervaluable properties, demonstrate a radical difference from like articlesof manufacture made from coagulated and milled rubber. Moreover, forcedextraction of the water from a latex, as by filtration under Ipressure-differential, breaks a considerable pro' portion, if not all,of the original rubber-particle units, and carries. off valuableingredients associated with rubber in latex.

There are still other methods than simple spontaneous evaporation of itsliquid by which a latex may be agglomerated, as by gradually acidifyingan alkaline latex .with an acid coagulant; the formation of a tube byagglomeration by such a method would require a technique more delicateand difficult than the evaporation method, which is therefore regardedas preferable.

Referring now to Figs. 5 drawings: In these figures there is illustratedan apparatus which in its essential members and their related operationsis the same as the ap-` paratus illustrated in Figs. 1 to 4,inclusive,'but shows adjunctive mechanical environment there- 4ofadapted to actuate the principal apparatus elements in the same manneras that described in connection with the explanation of the. process. Inthe apparatus as morefully equipped, the mandrels are multiplied, buteach.

in turn performs its function in relationto the latex trough orreservoir exactly as in the elementary arrangement and manipulation ofthe single-mandrel. In the intervals also between successive immersionsin the latex pool, each mandrel is rotated with relative rapidity andgiven time adequate to set the `last applied latex coating to the statedcondition which is short of that of reversibility of the surface. AThisapparatus is particularly designed to permit the .concomitantmanufacture of a plurality of tubes,

thus comprising supporting and conveying means which is arranged tocarry a plurality of rotary mandrels about a circuit, one part` of whichis in juxtaposition to a dipping vat that contains the liquid lwhich isto be applied to the mandrels in successive lms or layers.- zTo this endthe supporting means is preferably arranged to be locked inv a pluralityof positions, each one of which corresponds to the location `of one ofthe mandrels in juxtaposition to the dipping vat, whereby the supportingmeans may have an intermittent movement and be effective in bringingsuccessive mandrels into a position where the rotary surface thereof maycontact the liquid contained in the vat.

Preferably, means are provided to cause the Vat to be lifted to bringthe surface of the contained liquid into contact with a'narrow segmentalportion of a juxtaposed mandrel.

application of the latex layer or film to the mandrel, the speed of thelatter is preferably comparatively low'when its surface is in contactwith the liquid; while in order to permit the 4satisfactory drying ofthe latex or revertex and to permit the applied-layer of the same tomaintain a uniform thickness. without the occurrence of bubbles orwrinkles, thespeed of rotation of the mandrel is increased, i. e.,preferably factors such as electric motors for the mandrels,

to 8 inclusive, of the v Inl order to permit the effective, even, anduniform common source of 'supply by means of contacts'` engagingcircularor segmental conductors which" are arrangedso that themotor'thatdrives the mandrel in juxtaposition to the vat may rotate -ata 'lower speedV than the other motors.

As shown in Figs.' 5 and-6, the supporting and conveying means for themandrels may comprise a rotary frame or support l which is-provided withan axle 2-having its ends mounted upon supporting frames. or standards3; the support 1 -preferablypomprises parallel circular platesu 7 and7a,1which are spaced from each other at a .suitable distancefto permit.the. location of Y substantially rhorizontal cylinder. mandrels M. ofsuitable length therebetween. I

Preferably each :mandrel M comprises a hol-` low metal cylinder ofsuitable metal, such as aluminum, and has a comparatively smoothexterior surface. Plugs 12, provided with shoulders 9, are arrangedtointerfit withl the ends of the cylindrical ,mandrels, having centralopeningsv 8 ,for intertting engagement with axial sup-I ports thatarecarried by the parallel plates 7 and7axof rotary support 1.` Thus, asshown in Fig. .6, supporting plate 7 may carry a plurality of rotatableelements 18 mounted in and slidable` through openings 17; thesevelements havelieads,v 19 engaging sleeve-like stops 20that are securedto theplate 1... The opposite end of each rotatable ,element preferablyhas a frusto-conical head 21 that is` urgedby a spring 22 intointertting engagement with an opening 8 in a plug 12.. Each member-2oand opening 17 in plate l cooperate in providing a bearingv in which anaxialr support 18 may rotate. Y

At the opposite end of `each mandrel, we prefliov erably provide arotatable stub shaft 25 exizothrough gearing 26-27 in rotating thecorre.

sponding stub shaft 25 and the adjoining manv,dr el.. Obviously amandrel M may be removed bycompression of the corresponding spring 22and consequent movement of the. corresponding part 21 out of engagement.with the `plug 12,

ywhereupon the opposite plug may be4 removed from engagement with themember 21e.

AA vatfor trough T is disposed below axle -2 of the rotary support,being mounted upon a suitable frame 31, the ends of which are secured tonon-rotatable nuts 33 that-engage jackY screws 34 at either end of themachine. Theseljack screwsI preferably are verticallyY disposed androtate in Vbearing brackets 36 and 37 that are mounted on the standards3. The lower end of each jackscrewcarries a beveled gear 39 which mesheswitha corresponding gear 40 upon a horizontal shaft 41. Azhandcrank 44is' ar-A ranged to rotate'shaft 4l .byl means of sprockets 45` and 46.and 'a chain.47. It is thus evident that rotation of crank r44 is'effective in rotating shaft 41 andthe beveled.gears 39 and 40V to causethe jack screws 34 to turn. in unison, thus lifting .or lowering frame31 and'trough T.

Means are preferably provided to facilitate the stopping of the conveyormember or rotary .Y

frame yin any one. of a pluralityof positions cor-A respondingto Ythepreferred operative juxtal position of any one'of the rotary mandi-els M'La position!attheilowestLpontin its.path;. iae;, atv

.mandrel andaprogresses:rapidly 'tortheiother end5.

. locking. block 52 carried. by a.. plunger' 5.3.1 that.

is normally pressedl into; engagement. with. a. lug; by a. compressionspring; 514 (Figi: 7);. v-.A bracket 55 upon theirame; member; 3.supports.- tlre spring and plunger, while: a, handle: 56 permits its;movement out'. of'Y engagement; with the. lug. Preferably f the member5:2.A has a curved.; edge. pOrtion. 52L which.- permits. the ready?engagementoi; the side. of.thelug'withr.the locking block. as: the;frame; is rotated. the; lug snapping into engagement. Witlrthe..corresponding intermediate recess uponthe face of? the block to.

lock the frame in position; unless the; plunger is jmoved: or; held out.of.; its normalA position..

Ereferably each. of.: the. electric. motorsg29. re.- ceives. its.current. from .a common sourcebeing: connected.; tobrushes: Which-fare;mounted.- on..the.. rotatable plate 6.4:-.andi are resilientlyurgediinto.- engagement. with segmental conductors-6.0 and 60.a orclbwithin a 'xed contaotboxlv 61.. Pref-- erably. the.v inner. conductor6.()A is: circularu and:

may continually engage a brush=62that V:is con,- nected with. eachmotor,. the segmental. conduc-i tor. b f ormsthemajor portion of'acircle; the.

. short segmental. conductor Gila'being. located. be'V tweenits. ends;An individuali contact. 63'` forf v each. motor. thus is .normally i'nengagementwith either. the outer, segmental. conductor.r 60??V or thesegmental portion.60@;.there being. ashortfgapv of' non-conducting.vmaterial between thesev con-I ductors. Suitable. Variable resistanceszR1and' R2" may be arranged in series with. the conductors` 6l)a andf.6.01), .the resistance R21 in seriesl with. the Conductor 60?# being.arranged.I normally: to pro yidea; fairly. high resistance soithat.: thevoltage;-

of; the. current. flowing; through. the 'motor' 29 which; hasl its;brush;v 63 in. contact" with: the; conductor 60.a will be. materiallyless; than. that: passing: to the: remaining. motors; Preferably the;connections are so arranged. thatY less` en I ergy. will.: thus ybeimpartedto tl'lef.motorwhich is driving; the' mandrel. that.` has been.stoppedv in juxtaposition. to.: vat.. '12.. Under.y normali operating;condltions' the speed?Y of: each'-4 mandrel will therefore be;materially reduced. as it.v arrives ati a point.:.adjoining thevat'..

Preferably the axisa 2.: off the.- frame.- 7; andi the axes of" theindividuali rollers or..mandre1s: M are so disposed'. thati the 1latter. havefai slight. in

clination to -..the. surface ofi. the-.liquid contained.

Within: vatY T, i. a. slight: inclination: to. thel horizontal;v Thus,`the .lower.mostflimit;. or: longitudinalaprolla. of: the;` mandrel is.slightly dis-- placed from"parallelism.l with thek surface-1 off* liquidcomposition in thetro.ugl1:on-vat;i and,. wheny the; latter. is raised;to.l effect' immersion. of. the'. lower: sector of mandrel: surface.the. contact; between..y theJ lower liml of; the mandrel and. theYsurface.. ofi the; liquid. begins ailone'. endr; ofthe This mode.. of;makin'gi immersioni; isfiless likely.:

, toall'ow inclusioniof bubblesiinithe coating-.thanx immersionnofl theSentire. lower.' limb mandrel:r at.A the.. same... instant; r.

The; revertexconipositionts.which may: conta-in; forexamplezinc ox'id;nelydivi'ded sulfur'a'nd Y an; accelerator` is; placed: 1in-.the Vat?amfithei frame 1, as shown,A maybe rotated` by.' hand-forA .1

5 immerse;- thez lower.- limbo; ther mandrel in, and remorefitom; thelater.: @1191131.51011y in tbetroueh.-

any" suitableI intermittently operableuldriying; means mar beaemnloyedfor.thisnurnoseefthe..

support; f1. being; automatically' locked bythe blonli52fwhenfonefofithe mandrels M is brought.

intog juxtaposition With the vat. T.. Normally,

z thezflatter;r is disposed at. a4 level `which prevents.

thee conta'ct-ofzfsuch. a mandrel with the surface of' the contained;liquid;A YThe crank. Lidrnay then be;J operatedta lift; the; frame 3land vat. T' so` gressivecontacting of.l the; liquid surface with: thesurface off. the mandrel; which is eiective; in

forcing; outzairrfrom between these. surfaces and;

Which'layoidsfthe tendency .of airgclinging to. the

mandrel; to aform. bubbles or. blisters in.. the deifposited; nlm.. Themandrel. preferably is; per;

. initted to rotate for one revolution, thereby' piokingupfathin lmor/acoating. of'. the. latex or.' rei/.ertenf The handle. 44 is thenoperated, to lowerA the Vatrrom'. itspositionwhere the mandrel.y engagesthe vliquid surfaoeand. the frame 1r istrotatedso'-tl'iat: thesucceeding mandrelr is disposedlfabovethe- .Vat andV so that the coatedmandreliis-moved. outaof jurita-position..tov the vat.V

Thisautomatically resultadue to the arrange- Ament ofithe segmentalconductors, in the rotary acc'elerationof the last? coated mandrel. ThusthetmandreL while: being coated, may have a comparativelylow.speed-toperniit .the depositing. of' afthinilayerxfofiliquid uponitssurface; practioallysas soon. as .it-leaves :the liquid surface, therotary speedof .the mandrel is'v increased, thus preventing; theformation: of wrinklesror irregu-l lar ridges upon the mandrel, in otherwordsinsuringzthe'retention of ,-a-thinunif'o-rm film; The

higher? speed' at'. which ther mandrels` rotate after latex orf-theremoval of the excess: moisture;

vleaving the Vat alsolaids: inthe drying of' their Preferably thesupportisnotr rotated at such a l `rate asitobring the first' coated.mandrel into performed; there will4 ordinarily be a period ofvdelay'betweenathesuccessive mandrel coatings.

While; as` show-n', therotary support 1 andthe vat- SO-may both beiVmanually moved or operie ated, it is* evident ftliat automatic meansmayr be provided for either orboth of thesejpurposes.

lWe claim: Y Y

1. n apparatusof the character. descrilved,V ahorizontal"cylindric'allmandrelrotatably mounted with its. lowerinost.limit: slightly inclined to the .l horizontal, means .tdi-state thesame, atrough adapted .to.o'entail/1 .latex emulsion,v said troughvlocatedbelow' the said mandrel, rand,means -ier relatively.v movingl themandrel and .trough lteV immerse. .theflower' limb of; the mandrelv in,.and

renroyei-'itL-fromnthe vlatenerriulsion inthe trough. Y 2:;-Inlapparatusi-.oi' the :character described, a. horizontalcylindricalmandrel rotatably mounted:

with itslowermost` limiti. slightly inclined. to* the looatedf below..Ithesaidi mandrel, and. means for.l

relatively' mofa/'ing4 the f mandrel; and. trough to the means forrotating the mandrel adapted to impart different rates of rotationthereto.

3. Apparatus of the class described comprising a plurality of horizontalcylindrical mandrels, a common supporting and conveying means, saidmeans being arranged to move the mandrels about a circuit Whilepermitting their rotation about their individual axes, means forrotating the mandrels, a vat arranged to contain liquid to be contactedby the surface of each mandrel in one portion of its circuitous path,each mandrel having its axis slightly inclined to the horizontal as itis brought into juxtaposition to the vat, whereby its surface isprogressively brought into contact With the liquid surface.

4. Apparatus of the class described comprising a plurality of mandrels,a common supporting and conveying means, said means being arranged tomove the mandrels about a circuit While permitting their rotation aboutindividual axes, a vat arranged to contain liquid to be contacted by thesurface of each mandrel in one portion of its circuitous path, drivingmeans to cause the rotation of the mandrels and control means associatedwith the driving means, said control means automatically causing themore rapid rotation of a mandrel as it moves out of juxtaposition to thevat.

5. Apparatus of the class described comprising a plurality of mandrels,a common supporting and conveying means, said means being arranged tomove the mandrels about a circuit While permitting their rotation abouttheir individual axes, a vat arranged to contain liquid to be contactedby the surface or" each mandrel in o-ne position of its eireuitous path,locking means automatically operable to stop the supporting andconveying means in a plurality of positions corresponding to thelocation of the respective mandrels in juxtaposition to the dipping vat,driving means to cause the rotation of the mandrels and control meansassociated with the driving means, said control means automaticallycausing the more rapid rotation or" a man drei as it moves out ofjuxtaposition to the Vat.

6. Apparatus of the class described comprising a plurality of mandrels,a common supporting and conveying means, said means being arranged tomove the mandrels about a circuit while permitting their rotation abouttheir individual axes, a vat arranged to contain liquid to be contactedby the surface of each mandrel in one portion of its circuitous path,locking means to stop the supporting and conveying means in a pluralityof positions corresponding to the location of the respective mandrels injuxtaposition to the dipping vat, individual driving means for each ofsaid mandrels, and control means associated with said driving means andarranged to cause the more rapid rotation of each mandrel as it leavesthe vat and a decrease in its speed before being brought intojuxtaposition to the vat.

7. Apparatus of the class described comprising a plurality of mandrels,a common supporting and conveying means, said means being arranged tomove the mandrels about a circuit While permitting their rotation aboutindividual axes, a vat arranged to contain liquid to be contacted by thesurface of each mandrel in one portion of its circuitous path,individual driving motors for each of said mandrels, a common source ofcurrent for said motors, and conductors to transmit current from saidsource to the motors, a resistance in series With one of said conductorsarranged to cause the supply of a smaller amount o-f current to themotor that is driving the mandrel in juxtaposition to the vat than tothe other motors.

8. Apparatus of the class described, comprising supporting and conveyingmeans, a plurality of rotatable mandrels carried by said means, adipping vat arranged to contain liquid to be contacted by in turn therespective mandrels, means for rotating the mandrels, said means beingarranged automatically to effect the rotation of each mandrel at arelatively low speed when in juxtaposition to the tank, and at arelatively high speed thereafter.

9. Apparatus of the class described, comprising supporting and conveyingmeans, Y said means comprising spaced parallelly disposed portions, aplurality of rotatable cylindrical mandrels spanning Ythe space betweensaid support portions, driving means associated with one of said supportportions and comprising elements adapted to interiit With one end ofeach of the cylindrical mandrels and, axial elements carried by theother supporting portion and arranged to intert with the other end ofeach of the cylindrical mandrels, said axial elements each having acompressible portion, whereby the opposite end of the mandrel maybeimoved out of interfitting engagement With the corresponding drivingmember by the compression or" the said portion of its axial element.

ALFRED A. GLIDDEN.

THOMAS M. KNOWLAND.

